The sensory ecology of caterpillars

Caterpillars (larval Lepidoptera) are one of the most ecologically and evolutionarily significant taxa on Earth. As both feeders and food, they shape the dynamics of enumerate ecosystems on land. Key to this prominent role in nature is the sensory systems that inform, guide, and trigger their behaviour. Gaining an understanding of caterpillar sensory ecology therefore promises to reveal fundamental insights into the broader principles of ecology and evolution, conservation and management, within and beyond the Lepidoptera. To facilitate such an understanding, here we review the existing literature on the sensory physiology and ecology of all currently recognised sensory modalities in caterpillars, namely vision, hearing, vibration detection, touch, electroreception, chemoreception, hygroreception, thermoreception, and graviception. In each of these sensory modalities, we also explore the current evidence surrounding the threat of anthropogenic sensory pollution. Taken together, this review reveals the great depth and breadth of research into caterpillar sensory ecology, making clear the value of caterpillars to neuroethology, but also of neuroethology to caterpillars. However, many of the attributes that caterpillars bring to neuroethological research are yet to be taken advantage of. For example, there is currently a lack of comparative sensory system studies on caterpillars, utilising their ecological diversity and existing phylogenetic data. We also highlight many considerable knowledge gaps, most pertinently, the need to identify the sensors responsible for each sensory modality in caterpillars, and to characterise the potential effects of sensory pollution across all of these modalities.